A gas cylinder is generally adapted to a height ascending and descending structure of a sitting part of a chair on which a user sits, so a user can selectively ascend or descend the sitting part using a gas pressure.
The conventional gas cylinder is often called a gas spring and as shown in FIG. 1, comprises a hollow outer cylinder 10 vertically installed on a base provided on the ground, a bushing member 20 which is secured to an inner upper portion of the outer cylinder 10, a spindle 30 which slides and is inserted in the upward and downward directions at an inner side of the bushing member 20 and forms a gas flow path and is equipped with inner and outer pipes 32 and 34, a piston 40 which slides in the interior of the inner pipe 32 and ascends or descends the spindle 30 on the basis of gas pressure, a rod 50 which is fixedly secured to the center of the bottom of the piston 40 and the bottom of which is fixedly secured to the bottom of the outer cylinder 10, a valve body 60 which is secured to top of the spindle 30 and controls the spindle 30 to ascend or descend on the basis of the operations of a valve pin which controls the flowing direction of gas, and a lever which drives the valve pin 62.
The above described gas cylinder operates on the basis of the flow of gas. The gas in the upper and lower spaces formed about the piston 40 moves via the gas flow path formed between the vale body 60 and the inner pipe 32 and the outer pipe 34 on the basis of the operation of the valve pin disposed in the valve body 60, for thereby ascending or descending the spindle 30.
The above described gas cylinder is mainly adapted to a chair in a known way. When a user operates the operation lever, the spindle 30 comes to ascend or descend on the basis of the support of the rod 50, thus ascending or descending the sitting part.
However, in case of the above described gas cylinder, when the sitting part of the chair ascends, the spindle 30 slides along the inner wall of the bushing member 20, which makes the outer surface expose to the outside. At this time, liquid lubricant such as grease coated on the inner surfaces gets on the surface of the spindle 30, which liquid lubricant is provided for smooth sliding operation.
Since liquid lubricant such as grease is supplied from the outside for the sake of continuous sliding operations of the spindle, when the liquid lubricant gets on a predetermined thing or a user's hand, the exterior of the thing stained with the liquid lubricant looks bad.
In order to improve the above described problems, the applicant of the present invention filed a grease leakage prevention gas cylinder whose Korean patent number is 10-1233097.
In the above mentioned grease leakage prevention gas cylinder, there are included a bushing member which is secured to an inner upper portion of the outer cylinder, a cylinder which slides up and down in the interior of the bushing member and is equipped with an inner pipe and an outer pipe, a piston which is positioned somewhere in the inner pipe where it can slide and ascends or descends the spindle on the basis of gas pressure, a rod whose top is fixedly secured to the center of the bottom of the piston and whose bottom is fixedly secured to the bottom of the outer cylinder, a valve body which is secured to top of the spindle and controls the spindle to operate up or down on the basis of the operation of a valve pin which controls the moving direction of the gas, and a lever which activates the valve pin, in which construction a cover is secured to top of the bushing member for the sake of covering the bushing member, and a guide groove is formed in an inner circumferential surface of the cover along its surrounding, and a packing coming into contact with an outer surface of the spindle is engaged to the guide groove.
In the above described invention, the outer surface of the spindle which extends from the bushing member of the outer cylinder when it is applied to a chair or the like and allows the sitting part to ascend or descend is not exposed to the outside, so liquid lubricant such as grease does not leak outside with the aid of packing, thus obtaining good-looking exterior and cleanness.
In the above described structure, since the spindle reciprocates in upward and downward directions while it slides along the bushing member, the grease which leaks outside as it gets on the spindle is collected by the bushing member when the spindle descends, so the grease increases on top of the bushing member.